混凝土中钢筋锈蚀深度比值的概率分布模型研究

探究混凝土中钢筋表面坑蚀的分布规律,是进行锈损钢筋混凝土构件可靠性评价的必要前提。通过对掺盐钢筋混凝土试件长达2年的室外干湿循环试验,得到89根不同锈蚀程度的钢筋;对锈蚀钢筋逐根清洗、量取质量、量测及计算分析后,获得了89组钢筋最大坑蚀与平均锈蚀深度的比值,并以此作为钢筋表面锈蚀特征的分析指标,利用数理统计相关知识对该...     

坑蚀对钢筋混凝土梁抗弯承载力的影响

比较了均匀锈蚀和坑蚀对锈蚀钢筋混凝土梁抗弯承载力的影响,定义了描述钢筋均匀锈蚀和坑蚀的两种参数。用试验数据比较了两种参数和锈蚀钢筋混凝土梁剩余抗弯承载力的关系,指出仅仅用均匀锈蚀描述锈蚀钢筋混凝土梁的抗弯承载力是不够的,还应考虑坑蚀的影响。研究了不同坑蚀系数下均匀锈蚀率和坑蚀锈蚀率的关系,指出确定钢筋坑蚀量的关键在于确定坑蚀系数的值,对坑蚀系数的选取应当慎重。给出了同时考虑协同工作系数和坑蚀系数的锈蚀钢筋混凝土梁抗弯承载力的计算公式,公式的计算结果与14根梁的试验结果可以很好吻合,表明所提出的公式可用于既有混凝土梁剩余抗弯承载力的评估。     

钢筋坑蚀对混凝土梁抗弯性能的影响

与钢筋均匀锈蚀相比,钢筋坑蚀具有显著的不确定性和截面损失等特点,对混凝土构件的抗弯性能具有一定的影响。结合国内外相关资料,通过实际工程中钢筋坑蚀的试验统计,验证了坑蚀系数服从极值I型的分布。基于钢筋的坑蚀概率模型,借助MonteCarlo模拟,分析了锈蚀钢筋混凝土梁的抗弯承载力,研究了钢筋坑蚀对混凝土受弯构件承载能力的影响。结果表明,钢筋坑蚀的随机性对梁的可靠性有很大影响,钢筋坑蚀构件抗弯承载力的下降速度比均匀锈蚀更快,对梁的耐久性具有潜在危害。     

氯盐环境下混凝土内钢绞线的锈蚀特性试验研究

预应力钢筋的锈蚀特性是研究预应力混凝土结构耐久性失效及防治的基础，为此，分别采用内掺盐和外浸盐两种方式在自然气候条件下作了如下三组混凝土内钢筋锈蚀的对比试验：钢绞线与热轧带肋钢筋、钢绞线与热轧光圆钢筋、钢绞线中心钢丝与热轧光圆钢筋。通过对锈蚀过程中锈蚀电流密度的测试以及试验完毕后的破形观察与称重对比和分析，得到如下结果：钢筋外表面锈蚀程度在面向保护层侧明显严重于背向保护层侧；钢绞线及其中心钢丝外表面锈蚀相对最不均匀，具有严重的局部锈蚀——坑蚀形态，带肋钢筋次之，光圆钢筋相对最均匀、全面；钢绞线内表面发生类似于空气中的相对全面、均匀的锈蚀；钢绞线的平均外表面锈蚀率小于热轧带肋钢筋的与热轧光圆钢筋的，但严重的局部锈蚀对其受拉性能极其不利。另外，还对上述锈蚀特性进行了电化学机理分析。     

氯盐锈蚀钢筋的屈服强度退化分析及其概率模型

对混凝土内氯盐锈蚀HRB335级钢筋的坑蚀现象及其对钢筋力学性能的影响进行了研究;分析了现有拉伸试验中屈服强度判断方法的局限性,提出了锈蚀HRB335级钢筋名义屈服强度的判断方法(YPPCR法);将YPPCR法与数值分析相结合,建立了坑蚀钢筋数值拉伸试验方法;探讨了蚀坑三维尺寸对钢筋名义屈服强度退化的影响规律,建立了与蚀坑三维尺寸相关的单坑钢筋屈服强度退化的计算模型;最后对不同锈蚀率下由单个蚀坑引起的钢筋屈服强度的退化进行计算和概率分析,建立了与锈蚀率相关的钢筋屈服强度退化概率模型.     

氯盐腐蚀钢绞线蚀坑演化规律

为获得氯盐腐蚀钢绞线的坑蚀演化规律,采用通电腐蚀的方式得到了不同腐蚀程度的钢绞线,对其腐蚀特征和表面蚀坑形状及其规律进行了研究,将蚀坑形状归纳为四种类型,通过对蚀坑的统计分析,揭示了与锈蚀程度相关的蚀坑形状的发展演化规律。     

加速腐蚀环境下压型钢板力学性能的退化规律

通过加速腐蚀试验得到不同厚度、不同腐蚀程度的压型钢板板材试件,并根据三维表面形貌及拉伸试验结果分析表面粗糙度参数随腐蚀时间的变化规律、不同腐蚀程度试件破坏形态、应力-应变曲线差异、拉伸性能参数与腐蚀率的函数关系,建立了腐蚀压型钢板的性能退化本构模型.结果表明:试件表面粗糙度参数随腐蚀时间的增长呈阶梯状变化;随着腐蚀率的...     

海洋环境下锈蚀高强度钢材滞回性能

为研究海洋腐蚀对Q690高强度钢材(简称高强钢)滞回性能的影响,针对通过室内人工加速模拟腐蚀方法获得的Q690高强钢锈蚀试件,进行形貌扫描和循环加载试验,分析了不同腐蚀程度对其滞回性能的影响规律,建立了锈蚀钢材滞回曲线模型参数与其锈蚀率之间的关系.结果 表明:Q690高强钢抗震性能随腐蚀程度的增加而下降,腐蚀100 d后试件的滞回耗能降低15.2％,极限抗拉强度降低14.6％,锈坑深度达600 μm;采用Ramberg-Osgood模型可以较好地模拟锈蚀高强钢在循环荷载作用下的力学性能,该本构模型具有较好的实用性.     

地下巷道支护锚杆腐蚀状况调查及力学性能测试

 调查了河南焦作煤矿地下巷道腐蚀环境和现场10 a期管缝式锚杆腐蚀状况,对地下水腐蚀物含量、锚杆宏观质量损失和局部坑蚀情况实施了测量,并对锚杆杆体极限承载力和塑性性能进行测试。结果显示：未加任何保护措施的管缝式锚杆腐蚀较为严重,调查样本中的大多数锚杆寿命接近终结;锚杆外表面腐蚀状况以坑蚀为主,而内表面则以近似均匀腐蚀为主;锚杆表面的坑蚀数目、面积和深度等数据均遵循一定的散布规律,且坑蚀口部面积与深度间有内在关联;锚杆表面的坑蚀和穿孔对锚杆杆体力学性能有严重损害,而且锚杆延伸率损失率远大于极限承载力损失率,亦即腐蚀对锚杆塑性的损害程度远大于对其承载力的损害程度,这使得锚杆在发生破坏前难以监测到明显的变形,极易造成突发性事故。     

单调及循环荷载作用下锈蚀焊接钢板力学性能退化研究

文章为研究不同加载模式下钢结构局部焊接区域的力学性能退化规律,首先对5组Q235B对接焊缝连接钢板试件开展总周期长达12月的盐雾环境暴露腐蚀试验,采用三维形貌扫描技术对不同龄期、不同焊接区域锈蚀特征进行分析,随后对不同锈蚀程度焊接钢板试件开展单调及循环加载试验和数值模拟分析,详细研究锈蚀损伤及荷载类型等因素对焊接钢板受力行为、性能和失效模式的影响。研究结果表明：(1)局部点蚀深度随锈蚀深度的增大呈阶梯型增长趋势,受焊接过程影响,热影响区锈蚀速率略高于焊缝及母材区;(2)单调及循环荷载作用下锈蚀焊接钢板均在热影响区发生断裂,当锈蚀较为严重时,焊接钢板的断口形貌由韧窝断裂向剪切断裂转变;(3)循环荷载作用下,锈蚀焊接钢板强度、变形和耗能能力均呈现更显著的劣化现象,但锈蚀损伤对循环硬化效应的影响有限;(4)基于锈蚀特征参数建立的循环本构模型和等效循环延性断裂模型可准确模拟锈蚀损伤对焊接钢板受力性能及断裂行为的影响。     

A closed form formula to predict the ultimate capacity of pitted mild steel plate under biaxial compression

The aim of the present paper is to investigate the effects of pitting corrosion on the ultimate capacity of mild steel rectangular plates under biaxial compression, extending earlier results of uniaxially loaded plates. A series of non-linear FEM analysis of plates with partial depth corrosion pits are carried out, changing geometrical attributes of both pits and plates, i.e., the radius, depth and location of pits and the slenderness of plates. Simulation results show that volume loss dominates the degradation of the compressive capacity of pitted mild steel plates as well as loading ratio. Plate slenderness has considerable effect on biaxial interaction curve shape. A regression analysis of FEM results is conducted leading to a closed form formula able to predict the remaining strength of pitting corroded plates, where both volume loss and plate slenderness are taken into account. The proposed formula will facilitate a quick estimation of the remaining strength of pitting corroded plates during lifetime ship design phase which is relevant to maintenance decision-making of aging ship structures and components.     

A Time-Dependent Corrosion Characteristic of a Steel Member in Contact with Concrete

Steel members in composite structures of steel and concrete, such as composite girder bridges, guardrails, and steel piers, are often partially embedded in concrete members. The corroded steel members in contact with concrete were recently fractured because of corrosion damage. This study investigates the time-dependent corrosion behavior of a steel plate in contact with concrete by performing an accelerated cyclic corrosion test, which was specified in the ASTM D 6899-03, on four types of composite model specimens of steel plates with different painted areas and concrete blocks for 100, 200, and 400 cycles. The surface geometry of the corroded steel plates was measured at a 1?×?1 mm interval using an optical 3D measurement system after the corrosion productions were removed. The corrosion characteristic, that is, the changes in the corrosion growth, corrosion depth, and the corrosion depth distribution with testing time, was statistically analyzed. The application procedure of the present test results to atmospheric environments was also proposed based on the amount of flying salt.     

锈蚀对低碳钢滞回性能影响分析

以不同腐蚀程度Q235钢材试验数据为基础,运用数值模拟方法对锈蚀钢材的屈曲性能、滞回性能进行分析。结果表明,在循环荷载作用下,腐蚀试件屈曲最早发生在具有较大蚀坑的板材薄弱部位;随着腐蚀程度增加,屈曲现象明显,且提前发生;腐蚀钢材与未腐蚀钢材均出现循环硬化、峰值点指向效应等现象,但滞回环饱满程度明显降低,且腐蚀钢材各循环荷载性能指标均降低。     

Probabilistic deterioration model of high-strength steel wires and its application to bridge cables

Bridge inspections reveal that severe corrosion and fatigue are the main failure mechanisms of bridge stay cables. This paper presents an empirical modelling of the long-term deterioration process of steel wires in cables with consideration of the simultaneous occurrence of uniform corrosion, pitting corrosion and fatigue induced by a combined action of environmental aggression and cyclic loading. Accelerated corrosion experiments are conducted to determine the different corrosion levels of high-strength steel wires, and time-dependent statistical models are developed to quantify uniform and pitting corrosion depth. Corrosion-fatigue process of steel wires is subsequently simulated using the corrosion models and cyclic stress obtained through cable force monitoring data. The mechanical properties of corroded steel wires, including yield stress, ultimate stress, ultimate strain and modulus of elasticity, are experimentally characterised, and the statistical models are established through regression analysis. Finally, the deterioration models of high-strength steel wires (including crack depth, ratio of broken wires, and remaining strength, among others) is extended to probabilistically assess the time-variant conditions of bridge cables (sectional area loss and remaining capacity). The presented study on the long-term deterioration of bridge cables would provide guidance to future decision-making regarding the maintenance and replacement of bridge cables.     

一般大气环境锈蚀钢柱抗震性能试验与数值分析

为研究锈蚀对钢柱抗震性能的影响,对20个钢板试件和7个H型钢柱试件进行一般大气环境加速腐蚀试验.通过锈蚀钢板单调拉伸与低周往复加载试验研究锈蚀钢板单调与循环加载性能的差异性,揭示锈蚀钢材强度、延性退化规律,建立锈蚀钢材循环本构模型;通过锈蚀H型钢柱拟静力试验,研究锈蚀钢柱在地震作用下的损伤过程、破坏形态及性能退化规律,...     

锈蚀钢纤维力学性能及极限拉伸荷载计算方法

采用干湿循环法将钢纤维进行加速锈蚀,在分析其表观锈蚀特征的基础上,通过轴向拉伸试验和有限元分析研究了锈蚀程度对其力学性能退化的影响.结果表明:干湿循环处理后钢纤维表面出现了较多的锈坑,截面损失和锈坑处应力集中使其力学性能退化,而应力集中程度又取决于锈坑深度、宽度和钢纤维直径.建立了考虑锈坑深度、宽度和钢纤维直径影响的锈蚀钢纤维极限拉伸荷载退化模型,经试验验证,该模型也适用于计算锈蚀钢筋的极限拉伸荷载.     

考虑局部锈蚀特征的钢筋性能退化试验研究

采用电化学加速锈蚀和人工环境模拟方法制备侵蚀环境下混凝土构件中锈蚀钢筋样本,阐述了钢筋均匀锈蚀和不均匀锈蚀的发展机理,建立了更为合理的钢筋锈蚀程度分类方法和更为准确的评估指标.通过锈蚀钢筋力学性能测试,研究蚀坑参数对锈蚀钢筋力学性能的影响,建立了钢筋力学性能退化模型.考虑工程维护管理和结构性能评估实际情况,针对锈蚀率在5％～20％,蚀坑形状不规则的Ⅱ级钢筋,建立了蚀坑形状特征参数模型,为准确预测侵蚀环境下考虑锈蚀的钢筋混凝土结构长期承载力奠定了基础.